Process for producing tooth brushes and blanks for use for same

ABSTRACT

A process for producing a toothbrush produced thereby have the cavities (11, 12) arranged on the back side of the tooth brush head. The longitudinal axes (14a, 15a) for angling the head portions (13, 14, 15) relative to each other are arranged on or at the bristle-carrying side of the head portion directly opposite the associated cavity (11, 12). A blank for carrying out the process and a toothbrush produced thereby have the cavities (11, 12) arranged on the back side of the toothbrush head. The longitudinal axes (14a, 15a) for angling the head portions (13, 14, 15) relative to each other are arranged on or at the bristle-carrying side of the head portion directly opposite the associated cavity (11, 12).

With the present invention the particular aim is to be able to produce atoothbrush which is provided with groups of bristles arrnged so thatthese can produce effective cleaning of the surfaces of the tooth andadjacent gum portions including the depressions or the passages betweenthe tooth surfaces and the gum portions together with the intermediatespaced between the teeth.

First and foremost, the aim is a process with which the production canbe carried out as far as possible in a wholly automatised manner. Inthis connection, the objective is a process with which a tooth brush canbe produced which a) is effective in use and for one thing has a designwhich is compact and takes little space at the same time as it providesgood brushing effects, and which b) can be made in an accurate andreliable manner, with a favourable positioning of the groups of bristlesrelative to each other and, which c) can be designed so that the leastpossible collection of food residues, tooth paste residues, and the likeresults at the root of the groups of bristles.

According to the invention, a particular objective is a tooth brushhaving three head portions, that is to say a middle head portion and twolateral head portions which are arranged each on its respective side ofthe middle head portion and which are separated from the middle headportion by means of an intermediate passage portion with a cavity orattenuation groove.

Alternatively, tooth brushes can be designed with for example four, fiveor six separate head portions arranged in an angled or arcuatecross-sectional profile

The present invention is of particular interest in connection with theproduction of a tooth brush, such as disclosed in NO Patent Application880072 and U.S. Pat. Nos. 4,876,157 and 4,938,539, but is not limited tosuch a mode of production. In said patent application there is discloseda tooth brush construction where the second and third head portion areto be subjected, after the mounting of the groups of bristles in thedifferent head portions, to a first bending with a negative angle ofcurvature and thereafter to a second bending with a positive angle ofcurvature. The first bending with a negative angle of curvature isemployed in order to be able to cut the size and finally treat (polish)the groups of bristles to established, locally defined bristle lengthswith a single finishing equipment. The second bending with a positiveangle of curvature is employed in order to be able to fashion the headportions with their final angled contours relative to each other, whereit is decisive that the groups of bristles converge towards each otherin the manner precisely intended.

After the groups of bristles are placed in position in for example afirst, second and third head portion--while these head portions areflush with each other in the starting position--there is relativelylimited space for the heating equipment arranged between the groups ofbristles. With a negative bending of the head portions such as disclosedin NO Patent Application 880072, there is provided a better spacebetween the groups of bristles for the heating equipment prior to apositive bending of the head portions, that is to say prior to a bendingin an opposite direction to the negative bending effected by way ofintroduction.

With the hitherto proposed solutions, the cavities and the attenuationgrooves between the head portions on the bristle-carrying side of thehead are designed, so that with the subsequent positive bending to thefinal form the bending has been able to be effected at the same time asthe cavities become compressed, that is to say at the same time as thehead portions on the bristle-carrying side are pushed tightly togethertowards each other.

A problem with the last-mentioned solution is however that in thetightly pushed together grooves on the bristle-carrying side of the headportion there is a tendency for pockets to be formed for the collectionof food residues, tooth paste and the like.

With the present invention the aim is a solution where the head portionscan be arranged in such a manner that one is not dependent upon asubsequent pushing together of the head portions, but neverthelessobtains relatively tightly abutting head portions on bristle-carryingsides of the head, without collecting depressions for food residues andthe like and simultaneously the abundant possibility of access for theheating equipment independently of the groups of bristles of the head.

In practice it has proved difficult to be able to carry out themanufacture of a tooth brush according to NO Patent Application 880072with automatically operating production equipment. Particular problemscan arise in connection with the heating sequence just before and duringthe angling sequence. The problems arise mainly as a consequence of thelimited space at one's disposal in order to achieve effective heating ofthe angling region of the head of the tooth brush, while adjacentregions are to be spared as far as possible from such heating.

According to the known solution, one has chosen to place the cavities orthe attenuation grooves between the head portions on thebristle-carrying side of the head of the tooth brush in order to obtainthe best possible space for the heating equipment. By effecting theheating in said cavity or attenuation groove and thereafter carrying outthe bending to the final form, the V-shaped cavities can be clampedtogether at the same time into I-shaped slits and if necessary thesurface of the cavities melted together into continuous contact But thisis difficult to manage in a wholly automatic manufacturing process.

According to the known construction it can be crowded for space for theheating equipment in the introductory heating, while the introductory,negative bending however will result in an opening of the V shape, sothat better access is provided for the heating equipment from thebristle-carrying side of the head of the tooth brush to the cavities orthe attenuation grooves in the subsequent heating operation, prior tothe finishing, positive bending of the head portions.

With the present invention the aim is to achieve a better possibility ofaccess for the heating equipment to the bottom of the cavities or theattenuation grooves generally, that is to say both before a firstnegative bending and before a subsequent positive bending of the headportions, without complicating thereby the design of the tooth brushhead. Furthermore the aim is to be able to design the cavities or theattenuation grooves so that the heating can be restricted to the greatlylimited regions of the tooth brush head, that is to say mainly to thepassage portions between the head portions. By this there can beachieved a more rapid heating and a better controlled heating andthereby an increased possibility for rational manufacture of the toothbrush in a more or less wholly automatic production.

In the known constructions, with attenuation grooves or cavities on thebristle-carrying side of the head of the tooth brush, there is obtainedthe disadvantage that the groups of bristles which are localised tightlyup to the cavities or the attenuation grooves, have a tendency to loosenfrom their fastening in the tooth brush head as a consequence of thedeformation of the fastening holes of the groups of bristles produced byan undesired heating of the fastening regions or the groups of bristles.With the present invention the aim is to avoid this disadvantage.

The process according to the invention is characterised in that thecavities or the attenuation grooves are fashioned on the back side ofthe head of the tooth brush, that is to say on the side opposite thebristle-carrying side, and that the tooth brush head is subjected to alocal heating at the bottom of each of the cavities or the attenuationgrooves in that there is introduced in each cavity or attenuation groovea heat-conducting means for heating the cavity or the attenuation grooveat the bottom of same, after which the angling is effected about arespective one of said axes, which is arranged on or at thebristle-carrying side of the tooth brush head, just at the bottom of theassociated attenuation groove.

If high frequency heating is used, electrical conductors can be arrangedsimultaneously on opposite sides of the tooth brush head and effectiveheating of the intermediate portion at the bottom of the cavities or theattenuation grooves can be effected, without affecting adjacent groupsof bristles or their fastening points. With such high frequency heatinga spontaneous heating can be obtained as a consequence of the dielectricin the material right through the material in the intermediate portion.

If hot air heating is used, it is preferred that the heating is effectedlargely only or if desired in its totality from the back side of thetooth brush head and then as tightly as possible upwardly towards thebottom of the cavities or the attenuation grooves. In such a case, it ispreferred that the wall thickness between the head portions, that is tosay the wall thickness in the cavities is the least possible in order toobtain rapid through-heating of this wall portion. By employing arelatively thin-walled layer in the regions between the head portions,an especially rapid and effective heating can be obtained and acorrespondingly precise limiting of the heating to said regions betweenthe head portions.

The present invention also relates to a blank for producing a toothbrush according to the afore-mentioned process, including a tooth brushhead with at least three head portions, which are separated in pairsfrom each other by means of an intermediate cavity or attenuationgroove, the head portions being adapted to be angled relative to eachother about an axis parallel to an associated cavity or attenuationgroove after associated groups of bristles are fastened in place andafter a local heating of the tooth brush head is effected in the regionsbetween the individual head portions.

The blank according to the invention is characterised in that thecavities or the attenuation grooves are fashioned on the back side ofthe tooth brush head, that is to say on the opposite side of thebristle-carrying side, and that the axes for angling of the headportions relative to each other, are arranged on or at thebristle-carrying side of the head portion, directly opposite theassociated cavity or attenuation groove.

By placing the cavities or the attenuation grooves on the side oppositethe bristle-carrying side, several significant advantages are achieved.A first material advantage consists in the cavities or the attenuationgrooves being able to be employed as effective guide grooves for leadingthe blank from finishing station to finishing station. Another importantadvantage consists in the heating operation (especially by hot airheating) being able to be effected in its totality or for the most partfrom the side of the tooth brush head which lies opposite thebristle-carrying side. By this, the heating arrangement can beeffectively introduced in the associated cavity or attenuation groove inorder to ensure a concentrated and locally limited heating of thepassage portions between the head portions in the tooth brush head and acorresponding accurate positioning of the heating arrangement in theattenuation groove, without risking unintended heating of the groups ofbristles in the adjacent head portions.

According to the invention bending of the head portions can be obtainedrelative to each other precisely in the intended manner, by aconcentrated bending in the passage portion between two neighbouringhead portions. As a consequence of the accurate bending achieved, theneighbouring head portions can be fashioned relative to each other, sothat certain of the groups of bristles in the outer head portions can bearranged flush with or in between the groups of bristles in anintermediate head portion. One can ensure thereby that the groups ofbristles in neighbouring head portions can effectively support and braceeach other at outer ends of certain groups of bristles, while remaininggroups of brushes in the outer head portions are uncovered outside theintermediate head portion, without such extra bracing and extra support.Consequently, there can be ensured in a ready manner different brushingeffects for the groups of brushes of different head portions.

The present invention also relates to a tooth brush which includes atooth brush head with at least three head portions which are separatedfrom each other in pairs by means of an intermediate cavity orattenuation groove and which are angled relative to each other about anaxis parallel to an associated cavity or attenuation groove, rows ofbristle groups being fastened to respective head portions, with thegroups, of bristles in the one outer head portion obliquely disposedtowards the groups of bristles in the other outer head portion, wherethe groups of bristles have increasing bristle lengths reckonedlaterally from the middle portion of the tooth brush head outwardlytowards opposite longitudinal side edges of the tooth brush head andwhere certain bristle groups have bristles with larger bristle diametersthan the bristles in remaining bristle groups.

By the expression "bristle group" is to be understood herein a bunch orbundle of synthetically produced filaments formed with certainestablished lengths. The expression "bristle group" does not excludeother materials, such as pig bristles, horse hairs or other naturalproducts, but as a consequence of a lacking supply of such naturalproducts these usually get little application. By the expression"bristle group" is to be understood besides such a small bunch or bundleas there is space for in each associated hole in the tooth brush head.When one refers herein to the groups of bristles being arranged in"rows" this alludes to the groups of bristles being arranged accuratelyin rows. However it will be readily realised that the groups of brushescan be arranged in different ways that is to say more or lessirregularly, for example in a changing zig-zag path or in a similarmanner.

With the present invention the aim as mentioned is to achieve a bestpossible brushing effect for the tooth crown portion, the tooth sides,the intermediate spaces of the tooth and the depressions or the pocketsbetween tooth and gum with one and the same tooth brush by a simple anduncomplicated movement of the tooth brush relative to a row of teeth inthe mouth of the user. Furthermore, the aim is a design of the toothbrush head as favourable as possible both as to handling, strength andhygiene.

The tooth brush according to the invention is characterised in that thecavities or the attenuation grooves are arranged on the side oppositethe bristle-carrying side of the tooth brush head, and that the groupsof bristles in the middle head portion are terminated approximatelylevel with the groups of bristles in the innermost rows of bristlegroups of the two outer head portions.

An especially favorable solution consists in the groups of bristles withthe largest bristle diameter which in a manner known per se are mainlylimited to the middle portion of the tooth brush head--being arranged atleast in certain of the groups of brushes in the innermost row orinnermost rows of bristle groups of the two outer head portions, theinnermost row of bristle groups of the two outer head portions obliquelycolliding mutually or towards intermediately disposed bristle group(s)in an intermediately disposed head portion.

A further advantageous solution consists in the passage portions betweenthe head portions being graduated with a relatively shallow cavity orattenuation groove on the bristle-carrying side of the tooth brush headand an appreciably deeper cavity or attenuation groove on the oppositeside of the tooth brush head. By this one can nevertheless achieve witha restricted consumption of material great rigidity and strength ondifferent head portions of the tooth brush head relative to each otherand relative to the handle portion of the tooth brush.

Further features of the invention will be evident from the followingdescription having regard to the accompanying drawings, in which:

FIG. 1 shows a plan representation of a tooth brush blank seen from theback side of the blank.

FIG. 2 shows a cross-section of the head of the tooth brush blank aftergroups of bristles are set in position in the same.

FIG. 3 shows a detail of FIG. 2 on a larger scale.

FIG. 4 shows in a corresponding section to FIG. 2, said head after afirst bending with a negative bending angle is effected.

FIG. 5 shows in a corresponding section to FIG. 4 the head of the toothbrush after a bending with a positive angle is effected.

FIG. 6 shows in a representation corresponding to that shown in FIG. 2the tooth brush in a finally formed condition with associatedconsiderable enlargement of the grooves at the bottom of these.

FIG. 7 and 8 show a second embodiment illustrated in a sectioncorresponding to FIG. 2 and FIG. 5.

FIG. 9 and 10 show a third embodiment illustrated in a sectioncorresponding to FIG. 2 and FIG. 5.

FIG. 11 and 12 show a fourth embodiment illustrated in a sectioncorresponding to FIG. 2 and FIG. 5.

FIG. 13 shows in part a plan representation of a tooth brush headaccording to the invention.

FIG. 14 shows in a representation corresponding to FIG. 13 analternative construction of tooth brush head according to the invention.

FIG. 15 shows a tooth brush according to the invention schematicallyrepresented during brushing of a tooth.

In FIG. 1 there is shown a tooth brush blank 10 with a head 10a and ahandle 10b together with a narrowed neck 10c. On the back side of thetooth brush blank 10, as shown in FIG. 1, there are fashioned cavitiesor attenuation grooves 11 and 12 which extend in the longitudinaldirection of the tooth brush, that is to say parallel to the illustratedrectilinear sides 10b' and 10b" of the handle. The cavities of theattenuation grooves 11 and 12 partition the head 10a into threerectangular head portions 13, 14 and 15.

A first, middle head portion 13 extends essentially flush with andparallel to the neck 10c between the head 10a and the handle 10b. Asecond head portion 14 projects laterally outwards from the one groove11, while the other head portion 15 projects laterally outwards from thesecond groove 12. On each side of the neck 10c, that is to say in thetransition portion between the head portion 14 and the neck 10c, and inthe transition portion between the head portion 15 and the neck 10cthere extend rounded corner bracing portions 16 and 17, which are flushwith the associated cavity or attenuation groove and which have minimalwall thickness, that is to say a wall thickness corresponding to thewall thickness of the cavities or attenuation grooves.

As shown in the starting position of the blank in FIG. 2 the headportions 13, 14 and 15 are flush with each other. In each head portion13, 14, 15 there are designed a number of holes 18, which are arrangedin a number of longitudinal and transverse rows. In FIG. 2 there isshown only one transverse row of holes. More specifically there is showna row of two holes in the first head portion 13 and a row of four holesin each of the two remaining head portions 14 and 15. The number of rowsand the number of holes in each row is not critical and can be changedaccording to desire and need, but it is assumed that one or two holesare present in each row in the head portion 13, all according to whethera relatively small or a relatively large tooth brush is underdiscussion.

In each hole 18 there is inserted a group of bristles 19. Each bristlegroup 19 is, as is shown in FIG. 3, fastened in place in an associatedhole 18 with a fixing disc 20. The bristle group 19 is pushed intogether with the fastening disc in a manner known per se and secured inthe hole 18 by means of friction. As illustrated the inner end 19a ofthe bristle group is localised with the associated fastening disc 20 inthe bottom of the hole 18. As shown in FIG. 2, the bottoms 11a, 12a ofthe cavities or the attenuation grooves 11, 12 are arranged at a levelconsiderably above the level for the fastening disc 20 of the bristlegroup. The cavities or the attenuation grooves 11, 12 have a breadth aat the bottom 11a, 12a which substantially corresponds to the height bof the cavities or the attenuation grooves or of side surfaces 11b, 12bof these. The side surfaces 11b, 12b converge outwardly from therespective bottom 11a and 12a separately at an angle v of about 15°.

In FIG. 1 and 2 the attenuation grooves are shown with a maximum breadtha' which corresponds for example to the minimum breadth a plus 1 mm,while the attenuation grooves in FIG. 5 and 6 are illustrated with amaximum breadth a" which corresponds for example to the minimum breadtha plus 3 mm. Instead of getting a compressed attenuation groove in thefinally fashioned condition of the tooth brush head, according to theknown solutions with the attenuation grooves on the bristle-carryingside, there is obtained, as a consequence of a certain stretching actionin the material of the cavities or the attenuation grooves during thebending operation which follows the heating operation, a somewhatexpanded connecting portion between the head portions not only on theback side of the tooth brush head but also on the bristle-carrying sideof the tooth brush head.

According to the invention the tooth brush head can be designed todevelop relatively uniformly and without material gradations on thebristle-carrying side of the tooth brush head and can thereby avoid to alarge extent the collection of food residues, tooth paste residues andthe like, in the finally formed tooth brush head.

In the illustrated embodiment the head 10a has in the starting position(FIG. 1 and 2) a collected breadth of about 34 mm and a length (reckonedparallel to the handle 10b ) of 20 mm. The head portions 13, 14, 15 havea thickness of 5 mm. The head portion 13 has a breadth of 6 mm, whilethe head portions 14 and 15 each have a breadth of 12 mm. Holes 18 ofthe head portions 13, 14, 15 for the bristle groups have a depth ofabout 3.7 mm. The depth of each attenuation groove is of about 2.5-3.5mm, while the breadth a of each attenuation grooves is of about 2 mm.

In FIG. 4 the head 10a is shown after a heating of this is effected onits bristle-carrying side by means of a first type of hot air nozzle 20,while a second type of hot air nozzle 21 is received at the bottom ofthe attenuation grooves 11, 12 on the opposite side of the tooth brushhead. In FIG. 4 head portions 14 and 15 of the head 10 are shown bentover with a negative bending angle relative, to the head portion 13after a first heating of the regions in the cavities or the attenuationgrooves 11, 12 is effected. By a broken line 22 in FIG. 4 there isindicated a section line for cutting collected groups 19 of bristles inone and the same operation to established rows of different lengths,with the head in a negatively tent condition.

In FIG. 5 the head 10a is shown after it is heated anew, in a mannercorresponding to that described above, by means of the hot air nozzles10 and 21. The head 10a is shown in FIG. 5 bent over with a positivebending angle to the finally produced shape of the tooth brush.

In FIG. 6 there is shown the finally produced tooth brush 10' with theassociated tooth brush head 10a' in finally fashioned condition, that isto say after the head portions 14 and 15 are bent with said positivebending angle as shown in FIG. 5, and after the hot air nozzles 20 and21 are removed from the tooth brush. In the present embodiment hot airnozzles are employed as heat conducting means 10 and 21 for heating therespective bottoms 11a and 12a of the attenuation grooves 11, 12 with astream of hot air.

Alternatively there can be employed other types of suitable heatconducting means, such as high frequency heat conducting means. By meansof such high frequency heat conducting means direct dielectric contactcan be formed with heat conducting means on opposite sides of the toothbrush head, that is to say directly opposite the cavities or theattenuation grooves. In such an instance there is no need for specialscreening of the heating means, an effective local heating beingachieved with the electrodes only in the material in the bottom of thecavity or the attenuation groove.

In the illustrated embodiment the hot air nozzles 20, 21 are limited byheat insulating conducting means 20a and 21a which are to preventunintended heating of the groups of bristles and side surfaces 11b and12b of the attenuation grooves. The conducting means can for example beswept externally with cool air, as is indicated by arrows 23. By meansof the hot air nozzles 20, 21 and the heat insulating conducting means20a, 21a there can be ensured a controlled, local heating of the passageportions between the head portions 13 and 14 and between the headportions 13 and 15, while the head portions 13, 14, 15 at side surfaces11b, 12b of the attenuation grooves are kept moderately heated. By thisunintended deformation of the head portions 13, 14, 15 can be preventedat the same time as the accurate bending over of the head portions inthe intended manner can be ensured relative to each other.

In order to prevent the groups of bristles from being loosened from therespective holes, it is of critical importance that heating of sidesurfaces 11b and 12b of the cavities or the attenuation grooves isprevented and thereby heating of the head portions 13, 14, 15 is reducedor prevented, at any rate at the bottom of the holes 18, where eachbristle group is fastened with its respective metal disc. By means ofcrosses 14a and 15b there are indicated the bending axes for the headportions 14 and 15 respectively. In order to obtain a favourable placingof the innermost longitudinal row of bristle groups 19 in the headportions 14 and 15 relative to adjacent bristle groups in the headportion 13, it is of importance that the bending axis is placed in aregion near the cavity or the attenuation groove and more specificallyin a region which lies furthest from the head portion 13.

In FIG. 4 there is illustrated a moderately negative bending angle. Inorder to obtain greater differences in the lengths of bristlesinternally in the different head portions 14 and 15 and relatively tothe bristle length in the head portion 13 there can be employed a largernegative bending angle than shown in FIG. 4.

In FIG. 5 there is also shown a moderately positive bending angle. Inorder that the groups of bristles in the head portions 14 and 15 shallreach further round to each other there can be employed a largerpositive bending angle than shown in FIG. 5.

According to an alternative mode of manufacture the blank in the initialcondition can, instead of the design which is shown in FIG. 2, be madefor example with a negative bending angle as shown in FIG. 4, the groupsof brushes can then be filled directly into the head portion in theposition which is shown in FIG. 4. Thereafter, cutting of the groups ofbrushes is effected, as is shown by the rectilinear broken line 22 inFIG. 4. It will also be possible, instead of effecting the bending witha negative bending angle as shown in FIG. 4, to carry out cuttingdirectly in a starting position as shown in FIG. 2 by employing suitablefinishing equipment for this which forms a directly fashioned, concavecountersinking along the top of the groups of brushes.

Instead of effecting heating from opposite sides of the tooth brush headby means of hot air nozzles 20, 21 the heating can if desired beeffected prior to the bending with a negative bending angle only bymeans of the hot air nozzles 20, while in a subsequent heating step forbending the tooth brush head with a positive bending angle there can beemployed only the hot air nozzles 21. As shown in FIG. 5, the heating inthe bottom of the attenuation grooves can be limited to restrictedregions, as is shown by hatched edge portions. By this it can be ensuredthat the bottom of the cavities or attenuation grooves is heated to anespecially strong degree, and that it is extended during the bendingoperation to a positive bending angle mainly to layers of the passageportions between the head portions 13 and 14 and 13 and 15 adjacent thebottom.

In FIG. 7 and 8 there is illustrated a second embodiment. In FIG. 7there is shown a tooth brush blank 100 with a head 100a having anarcuate section line 122a produced by means of suitable finishingequipment from a starting position as shown correspondingly in FIG. 2.In FIG. 8 there is shown the finished design of the finally flexed toothbrush head 100' in a section corresponding to FIG. 5. In the embodimentaccording to FIG. 7 and 8 there are produced relatively deep cavities orattenuation grooves 11, 12 on the back side of the head of the toothbrush and oppositely disposed, relatively shallow cavities orattenuation grooves 111, 112 on the bristle-carrying side of the toothbrush head. As is shown in FIG. 8 an especially thin-walled passageportion is obtained between each pair of head portions 13, 14 and 13,15.

In FIG. 9 there is shown a third embodiment of a tooth brush head 110ahaving a concavely and convexly folded section line 122b, produced in astarting position as shown correspondingly in FIG. 2. In FIG. 10 thereis shown a design following from this of the finally flexed tooth brushhead 110a', shown in a section corresponding to that shown in FIG. 5.According to FIG. 9 the bristle groups in the middle head portion 13 arefashioned substantially longer than the adjacent groups of bristles inthe neighbouring head portions 14 and 15. By this the relatively longerand thereby somewhat softer or less rigid bristles in the head portion13 are supported in an effective manner in a wedge engagement betweenthe groups of bristles in the neighbouring head portions 14 and 15. Asshown in FIG. 10 certain bristles in the bristle groups in the headportions 14 and 15 are threaded locally inwardly between the bristles ofthe bristle groups in the middle head portion 13 for extra support andclosing off of the bristle groups of the middle head portion.

In the construction according to FIG. 9 and 10 there are shownespecially deep cavities or attenuation grooves 11, 12 on the back sideof the tooth brush head and instead of cavities or attenuation grooveson the bristle-carrying side of the tooth brush head there are shownconvexly arched beads 11a, 112a together with a thin-walled passageportion between the head portions 13, 14 and 13, 15 respectively.

In FIG. 11 and 12, there is shown a fourth construction of a tooth brushhead 120a, which is illustrated with five cavities or attenuationgrooves 121 which correspondingly define six separate head portions 123.In the illustrated embodiment there is illustrated only one bristlegroup row in each head portion, but the number of bristle group rows ineach head portion can be varied and if desired increased to two or more,according to need. Further, the bristles are cut in order to effect adecreasing height in a direction centrally of the blank.

Even if it is preferred to use thermoplastic materials with large shapedurability on heating up to or above 100° for producing quality toothbrushes according to the invention, thermoplastic materials can also beused according to the invention which permit flexing with a minimalsupply of heat energy. Thermoplastic shaping can then be achieved at atemperature of for example substantially below 100° and down towardsroom temperature, by employing material which tolerates bending on theapplication of sufficient force and which ensures that the tooth brushhead retains the flexed shape wholly or partly after bending, if desiredcombined with after hardening.

In FIG. 13 there is shown a tooth brush blank 30 with a tripartite head31, that is to say with three mutually angled head portions 31a, 31b,31c connected in pairs. The two outer head portions 31a and 31c areshown substantially rectangular with a rectangular distribution ofgroups of bristles 23a-23e, 24a-24e, 25a-25e and 26a-26e. In the middlehead portion 31b, which is also rectangular, there is shown a single rowof bristle groups 32a-32e, but in practice there can be employed forexample two (or more) rows of bristle groups in the middle head portion.According to FIG. 13 all the groups of bristles are shown in rowslongitudinally as well as sideways in the tooth brush head.

In FIG. 14 there are shown in a representation corresponding to FIG. 13two rows of bristle groups 32a'-32d' and 32"-32d" which extend mutuallyin rows longitudinally as well as sideways in the tooth brush head, butwhich in the lateral direction of the tooth brush head extend out ofalignment with the rows of bristle groups in the neighbouring headportions 31a and 31c. By this each bristle group in the middle headportion 31b can be threaded in between and supported by two neighbouringbristle groups in a respective neighbouring head portion 31a and 31c.

In the embodiments in FIG. 13 and in FIG. 14 there are shown a toothbrush blank with associated bristle groups which have bristles(filaments) of different rigidity. There is illustrated a section of atooth brush head with the blank illustrated in plan condition. Aftermounting associated bristle groups the tooth brush head is bent firstwith a negative angle and thereafter the groups of bristles are all cutin this negative angle position, in order thereafter to bend the headportions to the finally angled form.

According to FIG. 13 there are illustrated in the head portions 31a and31c inner bristle groups 23a, 23b, 23c, 23d, 23e (shown totally black)of a first type with relatively maximum rigidity and bristle groups 24c,25c, 26 (shown spotted) of a second type having medium rigidity togetherwith remaining bristle groups 24a, 26a; 24b, 26b; 24d, 25d, 26d and 24e,25e, 26e (shown totally white) of a third type with minimum rigidity Inthe head portion 31b there are shown bristle groups 32a-32e (shownspotted) of a second type having medium rigidity.

According to FIG. 14 there are shown in the head portions 31a and 31ctwo inner rows of bristle groups 23b-23d and 24b-24d (shown totallyblack) of the first type having relatively maximum ridigity andremaining bristle groups, including bristle groups 32a'--32d',32a"--32d" (shown white) of the head portion 31b of the third typehaving relatively minimum rigidity.

In an assortment of "bristles" or filaments of interest according to theinvention there can be employed for example the following fiveassortments each with its specific, bristle diameter, namely; A) 0.10mm, B) 0.15 mm, C) 0.20 mm, D) 0.25 mm and E) 0.30 mm. Of these theassortment D represents a first type of relatively rigid "bristle",while the assortment C represents a second type of more medium rigidityand the assortment B represents a third type having little rigidity orgreat softness The assortment A can for example be employed in admixturetogether with the assortment B in order to achieve especially soft andslightly rigid "bristles" in bristle groups of the third type, whilecorrespondingly the assortment E can be employed in admixture with theassortment D in order to achieve an especially rigid "bristle" inbristle groups of the first type. All according to need howeverdifferent mixtures of the assortments A-E can be chosen for thedifferent types of bristle groups.

The first type of bristle groups can for example consist exclusively ofrigid bristles that is to say bristles having a relatively large bristlediameter or of a predominant quantity of bristles of relatively largebust diameter and a smaller quantity of bristles of less rigidity(greater softness).

The second type of bristle groups can for example consist ofsubstantially half bristles of great rigidity and the remaining half ofbristles of small or more medium bust diameters.

The third type of bristle groups can for example consist of apredominant quantity of bristles of small bristle diameter and a smallerquantity of bristles of somewhat larger bristle diameter. Alternativelythe third type of bristle groups can consist only of bristles havingsmall bristle diameters.

By this the different bristle groups can be allowed to exert differentbrushing effects all according to the rigidity of the bristle group andall according to the locating of the bristle group in the tooth brushhead.

According to the invention certain bristle groups can be allowed toprovide extra supporting effect to neighbouring groups, whilecorrespondingly certain bristles in the different bristle groups can beallowed to exert a certain supporting effect for neighbouring bristlesin the bristle group in question.

In FIG. 15 it is made clear how some groups of bristles of the first andsecond type of bristle groups form support abutments sideways andendways against adjacent tooth surfaces 27a, 27b, while bristles in thethird type of bristle groups can extend along adjacent tooth surfaces27c and can effectively reach into a gum pocket 28 and into a toothintermediate space 29.

Tooth brushes of the afore-mentioned kind are advantageous in thatcertain bristle groups can brush the teeth and especially tooth crownsof the molars (chewing surfaces with depressions and grooves) at thesame time that remaining bristle groups can brush flanks (inner side andouter side) of teeth with tooth necks and in gum pockets in thetransition between tooth and gum, by movement of the tooth brushlongitudinally along the row of teeth. By means of a moderate rotationof the head of the tooth brush about the longitudinal direction of thetooth brush or the longitudinal axis of the tooth brush head outwardlyfacing and inwardly facing tooth flanks of the teeth can be brushed oneafter the other, at the same time that tooth crowns of the teeth withchewing surfaces are brushed with bristle groups at a different obliqueposition.

In order to obtain an effective, but at the same time gentle brushing ofthe gum pockets between the gum and the teeth and an effective brushingof the intermediate spaces between the teeth, it is of considerableimportance that the bristles have suitable rigidity and suitablesoftness in different regions of the tooth brush head. It has not beenpossible hitherto to adapt the rigidity and the softness of the bristlesin a satisfactory manner in one and the same construction, at the sametime that the different bristle groups acquire a favourable contourrelative to the different tooth sections, the gum and tooth intermediatespaces.

With usual tooth brushes having a planar tooth brush head and having anapproximately uniform bristle end plane one has hitherto employed a typeof bristle groups of rigid bristles in the middle portion of the toothbrush head and a type of bristle groups of soft bristles in theperipheral portion of the tooth brush head. With this type of toothbrush effective brushing of projecting edges of the teeth and relativelylarge surfaces of the teeth can be achieved as a consequence of the useof relatively rigid bristles in the middle portion of the tooth brushhead. At the same time the aim is to obtain a more gentle brushing withsofter bristles at peripheral portions of the tooth brush head, that isto say especially where bristles of the tooth brush head can come intocontact with the gum, to the extent these bristles are allowed to comeinto such contact with the gum. But such a known solution howeverprovides a less effective brushing in depressions of the teeth, in theintermediate spaces between the teeth and in the gum pockets between theteeth and the gum, and the relatively rigid bristles in the middleportion of the tooth brush head will directly prevent and counteractthat remaining bristles can penetrate within the plane of brushing whichis limited by the rigid middle bristles.

According to the invention the objective is also to arrange theconditions better for brushing depressions of the teeth and intermediatespaces between the teeth together with the pockets between the teeth andthe gum, at the same time as there is obtained an effective brushing ofprojecting edges of the teeth and relatively large surfaces of theteeth.

When different types of bristle groups with different rigidity arediscussed herein, this is to be interpreted in the widest sense, that isto say on the one side bristle groups each with its respective type ofclearly different bristles and on the other side bristle groups withdifferent mixtures of different bristles. The different groups ofbristles can generally also be considered as a collection of bristleswith mutually different forms and with mutually differentcharacteristics and if desired with considerable dimensional andmaterial deviations within each group of bristles of the first andsecond types of bristle groups and with if desired equivalent deviationsalso within each bristle group of the third type of bristle groups andwith clear deviations from type to type.

An important reason for being able to obtain better tooth brushingeffects with tooth brushes according to the invention is for one thingthat different densities and different geometries of bristles can beachieved in the middle region with the relatively short bristles than inthe edge regions with the relatively long bristles. By this therelatively short and rigid bristle groups in the middle region of thetooth brush head can be utilised in a specific manner to effectivelybrush chewing surfaces of the teeth and upper edge portions of the teethand simultaneously for the effective mutual support of neighbouringbristle groups. At the same time the relatively long and smaller rigidbristles can be utilised along peripheral portions of the tooth brushhead, and the like in another specific manner for effectively brushinggum pockets, tooth intermediate spaces and similar tooth regionsaccessible generally with difficulty.

Due to bristle groups with mainly similar contours in the two mutuallyangled head portions being collected with great density especially inthe middle portion of the tooth brush head, there is achievedsurprisingly enough minimal mutual bracing in the lateral direction insaid middle region, so that the bristles in the middle portion of thetooth brush head, in spite of everything, can be bent relativelyunhindered in the lateral direction, the bristles of the two maincollections of bristles crossing each other and being entangled inwardlybetween each other across the longitudinal direction of the tooth brushhead. With a load obliquely towards the longitudinal direction of thebristles in the middle region of the tooth brush head, the mutuallycrossing bristles can be swung relatively unhindered inwardly betweeneach other at the same time as the bristles are bent and thereby permitthe remaining bristle groups with softer and longer bristles to bepushed further inwards into depressions, hollow spaces and pockets, asis intended.

At the same time the mutually crossing and mutually tangled bristleswill shore each other up to a considerable degree longitudinallyrelative to the longitudinal direction of the tooth brush head. By meansof the second type of bristle groups (that is to say bristle groupsarranged sideways relative to the first type of bristle groups)especially the rigidity of the first and second bristle groups cancollectively provide a local bracing and thereby an extra buttressing ofthe third (softer) bristle group. In this way the different bristlegroups can be more easily bent in the intended manner laterallyobliquely outwards than longitudinally obliquely outwards, relative tothe surfaces which are to be brushed.

In the middle region of the tooth brush head there can be achieved bythis an effective brushing by means of bristles which form abutmentssideways against the brushing surfaces and by means of bristles whichform abutments endways against the brushing surfaces--and thenespecially at chewing surfaces of the teeth with associated grooves anddepressions--without preventing thereby that remaining bristle groups inthe regions outside the middle region of the tooth brush head, are ableto come into abutment against respective brushing surfaces. By employingbristle groups of mutually different rigidity and mutually differentsoftness there can consequently be produced according to the inventionadditional different support longitudinally and sideways, but at thesame time with great freedom to move in certain directions than in otherdirections and at the same time with greater resilience for the third(softer) bristle group and thereby a better brushing effect of the thirdbristle group. The afore-mentioned bracing and buttressing is favorablefor the brushing effects, without thereby preventing the differentbristles penetrating into tooth surface grooves, tooth depressions,tooth intermediate spaces and gum pockets. This freedom of movement ofmissing support in certain directions and greater support and lesspossibility of movement in remaining directions, is achieved partly bycontrolled rigidity of the different bristle groups and partly by thegeometry of the bristle in each bristle group together with the specialmutual geometry between the bristle groups of the mutually deviated headportions of the tooth brush head. Consequently one can, according to theinvention, geometrically orientate the bristle groups relative to eachother so that certain bristle groups which collide against each otherwithin at the longitudinal middle plane of the tooth brush head, form arelatively tightly condensed group of mutually crossing, relativelyshort (and thereby relatively rigid) bristles, while remaining bristlegroups which have greater length and generally less rigidity and whichthereby have generally a greater possibility for movement, get theirpossibility for movement adjusted with locally arranged bristle groupswhich provide local bracing and support for the remaining bristlegroups. Said bristle groups which are geometrically considered toprovide great rigidity in certain directions can be made still morerigid by employing especially rigid bristle material, without preventingthereby the brushing effect of longer (and thereby relatively softer)neighbouring bristle groups disposed outside.

I claim:
 1. A process for producing a toothbrush comprising the stepsofproviding a toothbrush blank having a central head portion and a pairof end head portions disposed in coplanar relation, a plurality ofbristles extending from each head portion on one side of the blank and aplurality of grooves on an opposite side of the blank, each groove beingdisposed between said central head portion and an adjacent end headportion; heating the blank in the region of the grooves while bendingeach end head portion relative to said central head portion in adirection to close the grooves; thereafter cutting the bristles to formrows of bristles of different lengths; and thereafter heating the bentblank in the region of the grooves while bending each end head portionrelative to said central head portion in a direction to open thegrooves.
 2. A process as set forth in claim 1 wherein heating of theblank is effected under flows of hot air applied to each side of theblank.
 3. A process as set forth in claim 2 further comprising the stepsof insulating the bristles from heat from the flow of hot air duringsaid first step of heating the blank.
 4. A process as set forth in claim1 wherein each end head portion is bent on an axis near each respectivegroove and spaced from the central head portion.
 5. A process as setforth in claim 2 wherein the bristles are cut along a common plane.
 6. Aprocess for producing a toothbrush comprising the steps ofproviding atoothbrush blank having a central head portion and a pair of end headportions disposed in coplanar relation, a plurality of bristlesextending from each head portion on one side of the blank and aplurality of grooves on an opposite side of the blank, each groove beingdisposed between said central head portion and an adjacent end headportion; and heating the blank in the region of the grooves whilebending each end head portion relative to said central head portion in adirection to open the grooves.
 7. A process as set forth in claim 6wherein heating of the blank is effected under flows of hot air appliedto each side of the blank.
 8. A process as set forth in claim 7 furthercomprising the step of insulating the bristles from heat from the flowof hot air during said step of heating the blank.
 9. A process as setforth in claim 6 wherein each end head portion is bent on the axis neareach respective groove and spaced from the central head portion.
 10. Aprocess as set forth in claim 6 which further comprises the step ofcutting the bristles extending from the head portions on an arcuatesection line prior to heating of said blank.
 11. A process as set forthin claim 6 wherein the blank has a plurality of shallow cavities on saidone side, each cavity being disposed opposite a respective groove toform a thin-walled section between each pair of head portions.
 12. Aprocess as set forth in claim 6 which further comprises the step ofcutting the bristles on a concavely and convexly folded section lineprior to heating of said blank.
 13. A process for producing a toothbrushcomprising the steps ofproviding a toothbrush blank having a pluralityof heat portions, a plurality of bristles extending from each headportion on one side of the blank and a plurality of grooves on anopposite side of the blank, each groove being disposed between adjacentheat portions; and heating the blank in the region of the grooves whilebending each head portion relative to an adjacent head portion in adirection to open the grooves.
 14. A process as set forth in claim 13which further comprises the steps of cutting the bristles to effect adecreasing height in a direction centrally of the blank.